The redistribution of heat, momentum and moisture within the lowest one to three kilometers of the atmosphere (boundary layer) is of importance for understanding the evolution and nature of phenomena from local scale weather to climate. There are gaps in our knowledge of exactly how the convective boundary layer and the accompanying convective clouds redistribute these quantities in the vertical. For atmospheric numerical models, it is important that boundary layer processes be accurately parameterized. In an field expedition in 1985, the Principal Investigator studied the nature of entrainment/detrainment in cumulus clouds in the marine boundary layer in rainbands off the coast of Hawaii. The Principal Investigator will extend her previous work will use the results to test existing parameterizations of the marine boundary layer. Further, she also plans to investigate suggestions emanating from recent studies that macroscopic properties of the marine boundary layer are determined in part by cloud condensation nuclei.//